1. Field of the Invention
The present invention relates to an apparatus and method for searching for a writable area, an apparatus and method for updating recording management information, an integrated circuit, and write-once information recording medium.
2. Description of the Related Art
Optical discs which are information recording media are sorted into several groups, depending on the recording characteristics.
An example of a write-once information recording medium, in which information can be recorded only once into the same recording area, is a write-once optical disc. Generally, write-once optical discs are highly compatible with reproduction-only discs, and are relatively inexpensive, and therefore are recently becoming widespread. Examples of write-once optical discs representatively include DVD-R, CD-R, and the like (“80 mm (1.23 Gbytes per side) and 120 mm (3.95 Gbytes per side) DVD-Recordable Disk (DVD-R)”, Standard ECMA-279, December 1998). As an exemplary write-once optical disc, DVD-R will be described below.
FIG. 1 shows a DVD-R disc 100. The DVD-R disc 100 comprises an R-information area 101 and an information area 102.
The R-information area 101 comprises a PCA (Power Calibration Area) 103 and a recording management area (RMA: Recording Management Area) 104. The PCA 103 is an area for performing OPC (Optimum Power Control). The RMA 104 is an area in which information for managing the recorded state of a data area 106 is recorded.
The information area 102 comprises a lead-in area 105, the data area 106, and a lead-out area 107. The lead-in area 105 and the lead-out area 107 are control information recording areas in which a parameter required for accessing the data area 106 is recorded. In the data area 106, user data is recorded. The data area 106 is divided into recording sections called RZones. Information indicating the recorded state of each RZones 161 to 163 is recorded in the RMA 104.
In the accompanying drawings, symbol #n (n is an integer) indicates a serial number of an area or information. The serial number of information is, for example, an update counter value. In FIG. 1, symbol #n indicates the serial number of an area.
FIG. 2 is a diagram showing the RMA 104. The RMA 104 stores at least one piece of recording management information (RMD: Recording Management Data) indicating the recorded states of RZones (e.g., RMD's 191, 192, 200).
An RMD is updated, for example, when a new RZone is generated or when a disc is unloaded from a recording/reproduction apparatus. An RMD is recorded from the beginning of the RMA 104. Therefore, the latest RMD 200 is recorded at the terminating end of the recorded area of the RMA 104 (immediately before an unrecorded area 190).
In the latest RMD 200, starting addresses 211 to 213 of RZones, and last recorded addresses (LRA: Last Recorded Address) 221 to 223 which indicate the last position of the recorded areas of the RZones. When no RZone exists or no information is recorded in an RZone, the corresponding LRA indicates 0.
The latest RMD is not recorded in the RMA 104 every time the LRA is updated. Therefore, for example, when a recording/reproduction apparatus is unexpectedly powered off, the position of a read LRA may differ from the true position lastly recorded. To avoid this, by searching for the border between a recorded area and an unrecorded area, a true position lastly recorded is detected.
FIG. 3 is a flowchart showing a procedure performed by a recording/reproduction apparatus from when the DVD-R disc 100 is loaded into the recording/reproduction apparatus until when information is recorded thereonto.
In step 301, the latest RMD 200 is read out from the RMA 104.
In step 302, the RMD 200 read out in step 301 is referenced, and a writable address (NWA: Next Writable Address) corresponding to a writable RZone is sought.
FIG. 4 is a flowchart showing details of a procedure in step 301 of FIG. 3.
In step 401, the starting address of the RMA 104 is designated as a search starting address for searching for the border between a recorded area and an unrecorded area.
In step 402, the recording/reproduction apparatus determines whether or not information has been recorded at a position irradiated with laser light, in sequence, based on a reproduced signal from the disc or the like, thereby searching for the border between a recorded area ranging from the search starting address, and an unrecorded area.
It is determined whether or not the address of the unrecorded area immediately after the border between the recorded area and the unrecorded area, which has been detected in step 402, matches the starting-address of the RMA 104 (step 403). When it does not match, it is determined that an RMD has been recorded, and the process goes to step 404. When it matches, it is determined that an RMD has not been recorded, and the process goes to step 405.
An RMD located immediately before an unrecorded area is the latest RMD. Therefore, an RMD immediately before the border detected in step 402 is read out and stored into the recording/reproduction apparatus (step 404).
When the address of an unrecorded area immediately after the detected border between the recorded area and the unrecorded area matches the starting address of the RMA 104, an RMD has not been recorded in the RMA 104. In this case, for example, the disc is determined to be brand-new, and a flag indicating such a state is stored in the recording/reproduction apparatus (step 405).
FIG. 5 is a flowchart showing details of a procedure in step 302 of FIG. 3.
In step 501, the next address of an LRA of a writable RZone contained in the latest RMD read out in step 301 is designated as a search starting address.
In step 502, the border between a recorded area and an unrecorded area is sought from the search starting address.
In step 503, the address of an unrecorded area immediately after the border detected in step 502 is determined as an NWA.
According to the above-described procedure, the NWA which is a true writable address is determined. Data is recorded from the NWA as a starting position in response to a recording instruction from a higher-level control means, such as a personal computer or the like.
FIG. 6 is a flowchart showing an exemplary method for distinguishing a recorded area from an unrecorded area, which are used in procedures in steps 402 and 502.
In step 601, the amplitude of a reproduced signal read out from an optical disc is detected.
It is determined whether or not the amplitude detected in step 601 exceeds a prescribed value (step 602). When it exceeds the prescribed value, the process goes to step 603, it is determined that an area irradiated with laser light is a recorded area. When the amplitude of the reproduced signal is equal to or less than the prescribed value, the process goes to step 604, it is determined that the area irradiated with laser light is an unrecorded area.
According to the above-described procedure, the border between a recorded area and an unrecorded area is sought.
Unlike write-once optical discs, information can be overwritten in the same area in rewritable optical discs. An example of a rewritable optical disc is DVD-RAM (see “120 mm (4.7 Gbytes per side) and 80 mm (1.46 Gbytes per side) DVD Rewritable Disk (DVD-RAM)”, Standard ECMA-330, December 2001).
FIG. 7 shows a DVD-RAM disc (4.7 GBytes) 700. The DVD-RAM disc 700 comprises a lead-in area 701, two spare areas 702 and 704, a data area 703, and a lead-out area 705.
In the case of DVD-RAM, an area incapable of recording/reproduction (i.e., a defective area) may occur during the production of the disc or due to scratch or stain on a surface of the disc, or the like. To prevent a reduction in system reliability due to the presence of a defective area, defect management is performed. In the defect management, when a defective area is detected in the data area 703, information which was supposed to be recorded into the defective area is recorded into the spare area 702 or 704. Defect management information (DMS: Defect Management Structure) for managing a defective area when the defective area is detected is recorded in defect management areas (DMA: Defect Management Area) 706 to 709 possessed by the lead-in area 701 and the lead-out area 705.
FIG. 8 is a diagram showing the DMA 706. The DMA 706 comprises a DDS (Disc Definition Structure) 801 and a DFL (Defect List) 802 as defect management information. The DFL 802 comprises defective area addresses 821 and 822 indicating the address of a detected defective area, and replacement destination addresses 823 and 824 in a spare area.
The same information as that in the DMA 706 is recorded in each of DMA's 707 to 709.
At present, defect management is not performed for a write-once optical disc, such as DVD-R or the like. As a semiconductor laser capable of outputting shorter-wavelength light is developed, the recording density of an optical disc is becoming higher. Therefore, a scratch or a stain on an optical disc is relatively large compared to a groove or a mark formed on the optical disc, likely leading to an increase in defective areas incapable of recording/reproduction.
As described above, an NWA is detected before recording for write-once optical discs. In this case, a recorded area is distinguished from an unrecorded area based on the amplitude value of a reproduced signal. A defective area has a low quality of reproduced signal, i.e., a reproduced signal having a small amplitude. It is likely to determine such a defective area as a writable unrecorded area.